1. Field of the Invention
The present invention relates to a process for producing crystalline oxytitanium phthalocyanine. More particularly, the present invention relates to a process for producing crystalline oxytitanium phthalocyanine of type-I which shows strong peaks in CuK.alpha. characteristic X-ray diffraction at Bragg angles (2.theta..+-.0.2.degree.) of 9.0.degree., 14.2.degree., 23.9.degree., and 27.1.degree..
2. Related Background Art
Phthalocyanine pigments have come to be employed extensively as catalysts, electrophotographic sensitive members, solar batteries, sensors, etc., as well as in conventional uses for coloration of paints, inks, resins, and the like.
Among the phthalocyanine pigments, oxytitanium phthalocyanine is known to have excellent characteristics for an electrophotographic material. The characteristics vary depending on the crystal form of the oxytitanium phthalocyanine. A variety of crystal forms of oxytitanium phthalocyanine are obtained depending on the minute differences of production conditions.
Oxytitanium phthalocyanines having different crystal structures produced under various production conditions were described, for example, in JP-A Sho-59-49544 (U.S. Pat. No. 4,444,861)("JP-A" refers to Japanese Patent Application Laid-Open No.), JP-A Sho-59-166959, JP-A Sho-61-239248 (U.S. Pat. No. 4,728,592), JP-A 62-67094 (U.S. Pat. No. 4,664,997), JP-A Sho-63-366, JP-A 63-116158, JP-A Sho-63-198067, JP-A Sho-64-17066, and so forth. The crystal forms described in the above patent publications, however, are obtained usually as a mixture, which involves difficulty in uniformity of the quality of the products. Accordingly, a method has been desired which gives a pure crystal form of oxytitanium phthalocyanine and many attempts have been made therefor. Processes for production of A-type or C-type crystal are described, for example, in JP-A Sho-63-364, JP-A Sho-63-365, JP-A Sho-63-37163, JP-A Sho-63-57670, JP-A Sho-63-80263, and so forth.
It is described in Japanese Patent Application No. Hei-1-189200 that the oxytitanium phthalocyanine is a crystal form having strong peaks at Bragg angles (2.theta..+-.0.2.degree.) of 9.0.degree., 14.2.degree., 23.9.degree., and 27.1.degree. in CuK.alpha. characteristic X-ray diffraction. Specifically I-type oxytitanium phthalocyanine, has excellent characteristics for electrophotographic sensitive materials. Although the I-type oxytitanium phthalocyanine can be readily prepared in laboratories according to the preparation method described in the specification of the above patent application, the process is not sufficiently satisfactory regarding the employed solvents, from the standpoint of industrial production. For example, regarding the solvent used in the milling treatment, the ether type solvents are flammable, and further may be explosive if peroxide is formed; the monoterpene type solvents are not readily available for general use; and the liquid paraffin requires a long time for the treatment and is not easy to handle because of its high viscosity.